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This work reports the chemical composition as well as the antibacterial, antifungal and antiparasitic activities of the leaf essential oil from Piper malacophyllum. The oil was extracted by hydrodistillation and analyzed by GC-FID, GC-MS and polarimetry. Among the 28 compounds identified, (+)-camphor was the major constituent. The essential oil showed activity against most of the microorganisms tested, especially antifungal action, with a MIC of 500 µg mL-1 against Trichophyton mentagrophytes and Cryptococcus neoformans. This is the first study reporting the composition and biological properties of leaf essential oil from P. malacophyllum.

Essential oils have been extensively studied in recent years as a natural source of new antimicrobial agents. In this work, essential oils of leaf and branch from Drimys angustifolia growing in Southern Brazil were obtained by hydrodistillation and analyzed by gas chromatographies with flame ionization detector (GC-FID) and with mass spectrometer (GC-MS). Drimenol and bicyclogermacrene were isolated by column chromatography from branch and leaf essential oils, respectively. Oils, isolated compounds and combinations of them were assayed against Gram-(+) and Gram-(-) bacteria. The oils showed to be more active against Bacillus cereus, with minimum inhibitory concentration (MIC) 125 and 250 µg mL-1 for branch and leaf oils, respectively, strongly inhibiting bacterial growth. Bicyclogermacrene was more active then drimenol, providing a MIC value of 167 µg mL-1 against B. cereus. Synergism was not observed in any of the combinations tested.

Due to the biological properties associated to the Baccharis genus and the limited information on its antimicrobial properties, the present work investigates the chemical composition and antibacterial, antifungal and antiprotozoal activities of the essential oils of two species, B. uncinella from Campo Alegre and B. semiserrata from Atalanta, both places located in Santa Catarina State, Southern Brazil. Oils were obtained by hydrodistillation and were analyzed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (GC–MS). The dry leaf essential oil yield from B. uncinella was 0.65% (m/m), and 0.50% and 0.22% (m/m) for dry leaf and twig from B. semiserrata, respectively. The main components in the oil from B. uncinella were α-pinene (9.0%), β-pinene (9.2%), limonene (11.5%), β-caryophyllene (13.2%) and spathulenol (9.3%). The following major compounds were identified in the leaf essential oil from B. semiserrata: α-pinene (4.3%), β-pinene (11.4%), limonene (6.7%), β-caryophyllene (8.2%), γ-muurolene (7.3%), bicyclogermacrene (8.0%), E-nerolidol (9.6%) and spathulenol (9.8%). Similarly, in the essential oil from the twigs were α-pinene (3.3%), β-pinene (7.9%), limonene (9.1%), β-caryophyllene (3.9%), bicyclogermacrene (6.0%), spathulenol (25.1%), caryophyllene oxide (8.0%) and globulol (5.6%). The antibacterial activity was determined by microdilution method. Baccharis uncinella oil was inactive for all bacteria tested and B. semiserrata twigs oil presented moderate activity against Staphylococcus aureus and the leaves weak activity against S. aureus and Bacillus cereus. The antifungal activity was determinate by the agar dilution method. Baccharis uncinella oil was active against M. gypseum, T. mentagrophytes, C. neoformans and M. canis. Both, leaf and twig essential oils from B. semiserrata were active against Microsporum gypseum, Candida albicans, Epidermophyton flocosum, Trichophyton mentagrophytes and Cryptococcus neoformans. Baccharis semiserrata leaf essential oil was also active against Trichophyton rubrum. In the antiprotozoal assays, leaf essential oil from B. uncinella gave an IC₅₀ of 223 μg/mL against Tripanossoma cruzi. Both leaf essential oils were active only at 500 μg/mL against Leishmania braziliensis.

The bacterial species Staphylococcus aureus presents a variety of resistance mechanisms, among which the expression of β-lactamases and efflux pumps stand out for providing a significant degree of resistance to clinically relevant antibiotics. The 1,8-naphthyridines are nitrogen heterocycles with a broad spectrum of biological activities and, as such, are promising research targets. However, the potential roles of these compounds on bacterial resistance management remain to be better investigated. Therefore, the present study evaluated the antibacterial activity of 1,8-naphthyridine sulfonamides, addressing their ability to act as inhibitors of β-lactamases and efflux pump (QacA/B and QacC) against the strains SA-K4414 and SA-K4100 of S. aureus. All substances were prepared at an initial concentration of 1024 μg/mL, and their minimum inhibitory concentrations (MIC) were determined by the broth microdilution method. Subsequently, their effects on β-lactamase- and efflux pump-mediated antibiotic resistance was evaluated from the reduction of the MIC of ethidium bromide (EtBr) and β-lactam antibiotics, respectively. The 1,8-naphthyridines did not present direct antibacterial activity against the strains SA-K4414 and SA-K4100 of S. aureus. On the other hand, when associated with antibiotics against both strains, the compounds reduced the MIC of EtBr and β-lactam antibiotics, suggesting that they may act by inhibiting β-lactamases and efflux pumps such as QacC and QacA/B. However, further research is required to elucidate the molecular mechanisms underlying these observed effects.